UPDATE: Family members identified the victim as Rosy Esparza; the Arlington police department released a statement saying that it did not find any foul play or criminality associated with the incident.

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A woman died while riding the Texas Giant roller coaster at Six Flags Over Texas in Arlington Friday. The cause of the accident has not been determined.

The woman has not been identified. Six Flags Over Texas spokesperson Sharon Parker issued a statement, saying that the ride would be closed pending further investigation of the cause. Some witnesses said that the woman's restraint was improperly secured. The rest of the park remains open.

Witness Kanisha Howell told CBS DFW that she and her daughter watched the woman fall out of her seat as the roller coaster reached a peak, and that it took emergency responders awhile to locate the woman.

Witness Josh Fleak tweeted, "Literally just witnessed someone fly off the Texas giant two seats in front of me." He also told a reporter that the restraints on the seat opened, causing woman to fly out.

Gabe Flores, another witness on the ride, said that the woman was accompanied by two family members. "The worst part in all of this is she fell off at the beginning so her family rode the rest of the ride knowing she fell out," Flores said.

Singer Bridgit Mendler, who was scheduled to perform at the amusement park on Saturday, announced via Twitter that she would cancel her show. "I am so sorry that I won't be able to see those of you who were planning on attending my show tomorrow and I hope you will understand the circumstances," she said.

The Texas Giant opened in 1990. It was closed in 2010 to replace its wooden track with steel rails, and it reopened in 2011. It reaches 14 stories high and has a drop of 79 degrees, which the Six Flags website claims is the steepest drop of any wooden coaster. The ride uses a bar restraint to secure passengers.

Another roller coaster, The Shock Wave, has been closed for a month while the park awaits a replacement part.